The Controversial Cope’s, Haeckel’s and Dollo’s Evolutionary Rules: The Role of Evolutionary Retrogradation

Abstract

The goal of this chapter is to discuss old problems and recent polemics related to the famous Cope’s, Dollo’s and Haeckel’s rules. The first concerns phyletic size increase: that sort of trend is observed in a multitude of phyla and shows several exceptions during periods of environmental stress. The second rule is discussed with some details because evolutionary reversions of trends are also frequent during stress episodes. The third trend, terminal addition, is very common and one can observe numerous cases where characters that are added late in phylogeny are also the first to be deleted during external stress phases. The addition of new elements at the end of ontogeny is frequently concomitant with size increases (Cope’s trend). There are many sorts of stress that are recorded in the stratigraphical data: major pollutions due to the development of massive volcanism (large igneous provinces), major climate changes due to plate tectonics, etc. Our main examples of reverse evolution are observed in nautiloids, conodonts, planktonic foraminifera, benthic foraminifera, ammonoids, silicoflagellids, corals, trilobites, etc.